This invention relates generally to an apparatus and method for forming flat-cut paperboard carton blanks into erected cartons, and more particularly, to an improved apparatus and method for transferring the erected cartons from a forming station to a takeaway conveyor.
Apparatus is known for forming flat-cut carton blanks into erected cartons. The paperboard carton blanks are generally of rectangular configuration having a bottom panel and opposing side and end panels connected therewith along fold lines. Locking tabs are provided on the end panels for engagement with slits provided on the side panels during the forming operation. Alternatively, the erected carton may be of the heat-seal type, as is also well known. Locking tabs on the panels, or the heat sealed panel areas, serve to maintain the cartons, with or without hinged covers, in erected condition for subsequent filling, lidding and/or closing operations.
In known carton forming apparatus, typically a feeder mechanism deposits a carton blank onto a die. A forming head, or plunger, of rectangular configuration corresponding to the erected carton size, then engages the carton bottom panel to force the blank in a descending forming stroke through the die. The die includes forming guides engaging the carton sides and end panels during passage of the forming head through the die. In this manner, the carton side and end panels bend along their fold lines into upright position relative to the carton bottom panel, and into engagement with the corresponding end and side walls of the forming head. The die also includes tab stripper members to force or strip the locking tabs into the slits. Alternatively, on heatseal cartons, hot air nozzles activate the plastic coating for sealing.
During further operation, the forming head descends completely through the die, where the spring loaded presser fingers, such as the type disclosed in U.S. Pat. No. 4,464,155 to Collura et al. (owned by the assignee of the present invention) are positioned to project slightly into the path of the forming head. As the forming head descends into an end-of-stroke position, the presser fingers snap past the carton side panels. Thereafter, the forming head ascends to receive the next in-line carton blank, and as it does the upper edges of the side panels are engaged by the bottom edge of the fingers. Since the carton is now positively arrested by the fingers, it is stripped from the forming head and dropped by gravity onto a takeaway conveyor below.
Due to this drop from the forming head, the relatively light weight carton characteristically bounces upon striking the conveyor. Because of this bounce, the cartons occasionally become misaligned, or tip over, usually resulting in a carton jam and the operator having to stop the machine. This problem is compounded if the bouncing carton is struck by one of the conveyor flights (pusher lugs attached to the conveyor chains) while bouncing.
Several methods and devices have been employed to alleviate this problem. One of the more successful approaches incorporates the use of suction cups on an oscillating picker arm. The suction cups, attached to a suitable vacuum source through a conduit or hose, engage the bottom of the erected container, and then the arm lowers it in a timed and controlled manner from the forming head. U.S. Pat. No. 3,602,108 to Vuilleumier discloses an apparatus of this type. The problem with this, or similar configurations, is that the takeaway conveyor, and thus the downstream portion of the packaging line must be slowed to allow the picker arm time to carry out its function in coordination with the forming head. This arrangement not only thus limits the output of the packaging system, but also increases the initial cost and the maintenance requirements.